/*
 * @(#)BooleanAttribute.java
 *
 * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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 */

package org.wso2.balana.attr;

import org.wso2.balana.ParsingException;

import java.net.URI;

import org.w3c.dom.Node;

/**
 * Representation of an xs:boolean value. This class supports parsing xs:boolean
 * values. All objects of this class are immutable and all methods of the class
 * are thread-safe.
 * 
 * @since 1.0
 * @author Marco Barreno
 * @author Steve Hanna
 */
public class BooleanAttribute extends AttributeValue {

	/**
	 * Official name of this type
	 */
	public static final String identifier = "http://www.w3.org/2001/XMLSchema#boolean";

	/**
	 * URI version of name for this type
	 * <p>
	 * This field is initialized by a static initializer so that we can catch
	 * any exceptions thrown by URI(String) and transform them into a
	 * RuntimeException, since this should never happen but should be reported
	 * properly if it ever does.
	 */
	private static URI identifierURI;

	/**
	 * RuntimeException that wraps an Exception thrown during the creation of
	 * identifierURI, null if none.
	 */
	private static RuntimeException earlyException;

	/**
	 * Single instance of BooleanAttribute that represents true. Initialized by
	 * the static initializer below.
	 */
	private static BooleanAttribute trueInstance;

	/**
	 * Single instance of BooleanAttribute that represents false. Initialized by
	 * the static initializer below.
	 */
	private static BooleanAttribute falseInstance;

	/**
	 * Static initializer that initializes many static fields.
	 * <p>
	 * It is possible identifierURI class field so that we can catch any
	 * exceptions thrown by URI(String) and transform them into a
	 * RuntimeException. Such exceptions should never happen but should be
	 * reported properly if they ever do.
	 */
	static {
		try {
			identifierURI = new URI(identifier);
			trueInstance = new BooleanAttribute(true);
			falseInstance = new BooleanAttribute(false);
		} catch (Exception e) {
			earlyException = new IllegalArgumentException();
			earlyException.initCause(e);
		}
	};

	/**
	 * The actual boolean value that this object represents.
	 */
	private boolean value;

	/**
	 * Creates a new <code>BooleanAttribute</code> that represents the boolean
	 * value supplied.
	 * <p>
	 * This constructor is private because it should not be used by anyone other
	 * than the static initializer in this class. Instead, please use one of the
	 * getInstance methods, which will ensure that only two BooleanAttribute
	 * objects are created, thus avoiding excess object creation.
	 */
	private BooleanAttribute(boolean value) {
		super(identifierURI);

		this.value = value;
	}

	/**
	 * Returns a <code>BooleanAttribute</code> that represents the xs:boolean at
	 * a particular DOM node.
	 * 
	 * @param root
	 *            the <code>Node</code> that contains the desired value
	 * @return a <code>BooleanAttribute</code> representing the appropriate
	 *         value (null if there is a parsing error)
	 */
	public static BooleanAttribute getInstance(Node root)
			throws ParsingException {
		return getInstance(root.getFirstChild().getNodeValue());
	}

	/**
	 * Returns a <code>BooleanAttribute</code> that represents the xs:boolean
	 * value indicated by the string provided.
	 * 
	 * @param value
	 *            a string representing the desired value
	 * @return a <code>BooleanAttribute</code> representing the appropriate
	 *         value (null if there is a parsing error)
	 */
	public static BooleanAttribute getInstance(String value)
			throws ParsingException {
		// Shouldn't happen, but just in case...
		if (earlyException != null)
			throw earlyException;

		if (value.equals("true"))
			return trueInstance;
		if (value.equals("false"))
			return falseInstance;

		throw new ParsingException("Boolean string must be true or false");
	}

	/**
	 * Returns a <code>BooleanAttribute</code> that represents the boolean value
	 * provided.
	 * 
	 * @param value
	 *            a boolean representing the desired value
	 * @return a <code>BooleanAttribute</code> representing the appropriate
	 *         value
	 */
	public static BooleanAttribute getInstance(boolean value) {

		// Shouldn't happen, but just in case...
		if (earlyException != null)
			throw earlyException;

		if (value)
			return trueInstance;
		else
			return falseInstance;
	}

	/**
	 * Returns a <code>BooleanAttribute</code> that represents a true value.
	 * 
	 * @return a <code>BooleanAttribute</code> representing a true value
	 */
	public static BooleanAttribute getTrueInstance() {

		// Shouldn't happen, but just in case...
		if (earlyException != null)
			throw earlyException;

		return trueInstance;
	}

	/**
	 * Returns a <code>BooleanAttribute</code> that represents a false value.
	 * 
	 * @return a <code>BooleanAttribute</code> representing a false value
	 */
	public static BooleanAttribute getFalseInstance() {

		// Shouldn't happen, but just in case...
		if (earlyException != null)
			throw earlyException;

		return falseInstance;
	}

	/**
	 * Returns the <code>boolean</code> value represented by this object.
	 * 
	 * @return the <code>boolean</code> value
	 */
	public boolean getValue() {
		return value;
	}

	/**
	 * Returns true if the input is an instance of this class and if its value
	 * equals the value contained in this class.
	 * 
	 * @param o
	 *            the object to compare
	 * 
	 * @return true if this object and the input represent the same value
	 */
	public boolean equals(Object o) {
		if (!(o instanceof BooleanAttribute))
			return false;

		BooleanAttribute other = (BooleanAttribute) o;

		return (value == other.value);
	}

	/**
	 * Returns the hashcode value used to index and compare this object with
	 * others of the same type. Typically this is the hashcode of the backing
	 * data object.
	 * 
	 * @return the object's hashcode value
	 */
	public int hashCode() {
		// these numbers come from the javadoc for java.lang.Boolean...no,
		// really, they do. I can't imagine what they were thinking...
		return (value ? 1231 : 1237);
	}

	/**
     *
     */
	public String encode() {
		return (value ? "true" : "false");
	}

}
